The field of the disclosure relates generally to rotary machines and, more particularly, to systems and methods for use in controlling flow valves in turbines.
At least some known rotary machines convert steam thermal energy into mechanical rotational energy that is used to power a machine such as an electric generator. For example, known steam turbines typically include a high-pressure (HP) section and/or a reheat or intermediate-pressure (IP) section that each receive high-pressure and high-temperature steam. The steam is channeled through rows of rotor blades or turbine stages to induce rotation of a rotor assembly that is coupled to a load. The flow of steam is typically controlled by at least one flow valve that regulates and controls the steam flow entering the steam turbine.
At least some known steam turbines control power output through use of a control algorithm. A flow command, which is a percent value with 100 percent being full power, is transmitted to a flow-stroke conversion block that outputs a stroke command, also as a percent value. The stroke command is transmitted to a valve position control that selectively positions the flow valve. Within such systems, raw flow-stroke data, measured in pounds-mass per hour (lbsm/hr) for flow rate and inches (in) for valve stroke position, is normalized into a percent value. Because the valve position control receives the stroke command as a percent value, the valve position control requires a valve range to be in a percent value as well.
For at least some known steam turbines, the requirement to convert raw data into percent values may increase the overall complexity, implementation time, and costs associated with system development, commissioning and calibration, and uprating. Moreover, depending on the system, opportunities for calculation errors may be introduced.